Saturday, February 05, 2011

Router introduced noise in files

Even after sixteen years on the Net, I can still hear about new things. A customer of mine was having trouble with corrupted files he downloaded. In the end he found out that when he bypassed his router and plugged his computer directly into the modem, the problem disappeared! Huh. It seems the router introduced noise in the files. I would have thought that this would either be impossible or be very common, given the number of devices files fly through on their way around the Net.

BTW, I just got a new router yesterday. Virgin Media has given it the grandiose name The Superhub! And it does look a lot better than the old cable modem I had from them. And not the least, it has built-in not only wireless, but also an ethernet hub, so that was three devices I could unplug and replace with only one, pretty kewl.
I got it as part of a deal to upgrade from 20Mb to 30Mb. I don't expect to see much difference in practice, but on principle I just go with the best, roughly. It was just a smallish one-time fee.
It was also nice that Net connection, the wifi, and the ethernet all worked perfectly right off the bat, I love when that happens. (Only odd that it was mandatory to phone them up to get it registered and activated, that should not be necessary these days.)


Pat McGee said...

Re corrupted files: There are two common protocols for file transfer: TCP and UDP. TCP does error correction and detection; UDP does not. Web servers do UDP; file transfer programs like FileZilla use FTP.

FTP was designed for applications where error-free transfer was more important than speed of transfer; UDP was designed for cases where, if a bit is late, it is useless. (Think streaming audio or video.)

Both protocols were designed back in the day when most data traveled over phone lines at 1200 baud or (gasp!) 2400 bps. Analog noise was a big problem, and errors were measured in lost frames per minute. Now we send data over fiber and error rates are (comparatively speaking) infintesimal.

Personally, I think that web content should be delivered using FTP instead of UDP, but nobody asked me. In the original vision, they thought getting someone to hit the refresh button if something looked wrong was acceptable.

But, even with all that, the router must have been seriously hosed to fail like that.

eolake said...

It must have been.

Thank you very much.

ttl said...

Pat, I recommend you read a little more about said protocols. What you write is not all factually correct.

Web content is not delivered over UDP, but rather HTTP that uses TCP for transport.

FTP is not a very well designed protocol. For example, by default it opens two links to the server, whereas HTTP uses just one. There are other issues as well. HTTP is much simpler and lighter.

Tim Berners-Lee introduced many truly stupid ideas into WWW, but moving the transfer over from HTTP to FTP would not solve any of them. It would only make everything slower.

Eo, the problem could also have been a faulty cable.